how to change size and background of text

I have fooled with the various settings and options numerous times. I have a lot more images to load, but need to get this figured out first.

The slideshow is working the way I want it (changing size, including title and description) except for these two properties:
Way too big. I want it to fit on the page of, say, a 15" laptop.
Background of title and description to black with some transparency.

I have changed the setting numerous times for scaling, not scaling; auto height; not auto height, etc., and I guess I am just not hitting on the right combination of options.